In all printing machines, the majority of the cylinders are provided with displacement members enabling the cylinders to be spaced apart from one another, particularly in the case of absence of sheets to be printed or of adjustment of the machine. Such spacing apart corresponds to a displacement of low amplitude.
A displacement of certain cylinders, of greater amplitude, is sometimes necessary, particularly when it is question of changing one cylinder by another.
A number of devices have already been proposed for rapidly and easily changing certain cylinders. It may be question of a device outside the printing machine, for example in the form of a robot, such as the one described in document EP 0 400 517. It may likewise be question of devices integrated in the printing machine. Such a device for automatically changing cylinders in a flexographic printer is described in document FR 2 485 990. This device aims more particularly at automatically changing the plate cylinders and ink rollers on a flexographic printer whose impression cylinder is common to a plurality of inking stations. It comprises gripping means adapted to effect a certain disengagement of the cylinders in height, said gripping means cooperating with tiltable runways intended to ensure a linear translation of the cylinders, moving by gravity over the runways until they reach a position where they are adapted to be taken by pulley blocks.
In Applicants' opinion, the device described in this document FR 2 485 990 presents a certain number of drawbacks. On the one hand, it is very complex from the production standpoint, employing a very large number of various mechanical members. In addition, it is not totally automatic, insofar as a manual intervention is necessary to release the cylinder which it is desired to change.
It is an object of the present invention to propose a printing machine equipped with a plurality of cylinders and which comprises displacement means for at least one of said cylinders, which overcomes the drawbacks set forth hereinabove.